Spin-on filters have been employed in a variety of applications including hydraulic systems, fuel systems and lubrication systems. Such filters generally include a filter element positioned within a can, casing or housing having a cover or top plate at one end thereof, by which the filter can be mounted on a filter head. A central opening and several surrounding openings in the cover are usually provided to direct flow through the filter and filter element therein, which flow can be in either an inside/out or an outside/in pattern. A circular gasket on the outside of the cover serves as an external seal between the filter and the filter head. A second circular gasket on the inside of the cover functions as an internal seal between portions of the filter element and the cover. Spin-on filters are typically intended to be used only once, with removal and replacement.
In the past, two conventional arrangements have generally been used to provide for sealing engagement with respect to fluid flow outwardly from between the cover or top plate and the casing. An example of one of these types of conventional arrangements is shown in U.S. Pat. No. 4,369,113, the specification of which is incorporated herein by reference. For the arrangement disclosed in that patent, the cover (28) includes an outer rim or edge with an O-ring receiving groove therein. A circumferential O-ring (42) is positioned between the cover (48) and the housing (12) to provide the seal. Thus, the arrangement uses a positive seal positioned between the two assembly members which comprise the cover (28) and the housing (12).
Such an arrangement, while effective, is not completely satisfactory for all applications. First, a relatively thick and strong material may be necessary for the formation of the casing, since the casing should not be permitted to substantially deform in the area of the circumferential O-ring (42) or leaking may result. Such deformation, from metal fatigue for example, could follow a multi-pulse occurrence of relatively high fluid pressures within the filter assembly. Further, the arrangement of '113 generally requires a folded connection (47) in the top portion of the housing, which may be relatively expensive to prepare. Also, the arrangement provides for two possible locations of fluid leak, one around the seal provided by the O-ring (42) and a second around the seal provided by gasket (44) positioned between the cover plate (28) and the filter head. Two possible positions of leakage are almost inherently worse than one, and at least usually require more examination during use and care during assembly. Further, such an arrangement generally requires construction of the top plate or cover (28) from non-porous materials so that leaking through the material itself does not occur.
A second conventional method of providing sealing engagement with respect to flow from between a top plate and a housing or casing is illustrated in FIG. 1 herein. Referring to FIG. 1, reference numeral 1 generally designates a conventional filter assembly. The filter assembly 1 includes an outer casing 2 having an end 3, in which is received the cover, end plate or top plate 4. Details concerning the filter assembly 1 will not be described here, however generally the top plate 4 includes first and second flow means, or apertures 5 and 6, providing means for directing fluid flow into and out of the filter assembly 1. Generally, in use the filter assembly 1 is attached to a conventional filter head, (not shown) with gasket 7 providing for sealing engagement therebetween.
The flow seal for the casing 2 with respect to flow between the casing 2 and the top plate 4 is generally indicated by reference numeral 10. The particular seal 10 shown is a conventional roll type seal or seam 11. Such a seal is formed by welding or otherwise attaching plate 12 to an upper surface of the top plate 4. Plate 12 includes an extension 13 which may be rolled with an upper lip 14 of the casing 2, to form the seal 11.
Such a conventional roll-type seal may be undesirable for numerous reasons. For example, such a seal may work itself loose, and leak, under filter asembly use conditions, for example when numerous pulses of fluid under pressure flow through the assembly. Further, such an arrangement generally provides for two locations of potential leaking; one by means of flow passage through the roll seal 11 itself; and, a second being around the gasket 7 whereat the filter head, not shown, is engaged. Also, a roll-type seal may result in a substantial weakening of the casing material, as the multiple folds are formed. Thus, in some instances a relatively thick and strong casing material may have to be chosen, to help deter the roll-type seal from working itself loose. This may add cost or create special assembly needs. Further, top plates utilized in association with such roll seams must be of substantially rigid construction since the roll seams can loosen and leak under multiple pressure pulsations, if the top plate is flexible.
Another potential problem with such an arrangement is that generally the material chosen for the top plate should be such as to provide for a ready attachment of the plate 12 used to form the roll seal 11. Typically, plate 12, being steel, will be attached by spot welding, so the top plate 4 should be of a material, typically also steel, permitting such spot welding. This can lead to relatively expensive or corrosion prone components for the conventional filter assembly. Spot welding aay also result in contaminating fumes during construction.
A problem addressed by some conventional filter assemblies is that of providing lock means preventing the casing or housing from being rotated independently of the cover or end plate. Generally, a filter assembly is mounted for use by being spun onto a mount of a filter head or the like. Secure attachment is provided by threaded engagement between the top cover and the filter head. As the assembly is spun, unless a good tight engagement between the top cover and the casing is provided, the casing and cover may loosen and slip with respect to one another. One solution to this problem was suggested in U.S. Pat. No. 4,369,113 and relates to the utilization of projections on the top cover which are received in pre-formed indentations located in the housing. When the top cover is mated with the housing during assembly, generally the projections on the top cover are aligned with the indentations in the housing, before the insertion. Thus, assembly of an arrangement such as that shown in '113 may require a step of aligning the cover plate projections with the housing indentations, a potentially time consuming operation. Generally, it would be preferred to utilize an arrangement and method of assembly which could avoid this step and the costs associated therewith. Further, the arrangement of '113 generally requires expansion of the casing at an end thereof. This leads to a workhardening of the steel casing at this point, which makes folding of the metal, to retain the top plate, somewhat more difficult and potentially more expensive.